Zaman MALEKZADE - PhD, Payame Noor University, Tehran, Iran

Seismicity in Zagros Fold and Thrust Belt is known as an enigma Most of the located earthquakes lay between sedimentary cover rocks and basement in upper crust located in depths of 10-15km Subduction of Arabian plate has not been confirmed by geophysical investigation or by GPS measurements Indeed, the suture zone is not tectonically active as it is usual in area of continental underthrusting The decision making to attribute earthquake events to cover or basement is also debated Geophysical and geological studies across the belt, however, detected a weak thickened lower crust The role of a fluid lower crust and its interaction with upper crust is known as an interested subject in continental collision domains in last two decades With the use of bouguer gravity anomaly obtained by Snyder and Barazangi (1986) and calculating admittance and coherency, this study puts documents forward to show (in Zagros) the upper crust and lower mantle decoupled It then concludes the vertical pressure induced by lower crust injection and horizontal pressure running by Arabia is responsible for recent configuration of seismic activity in Zagros Finally, this paper discusses why the seismicity is different in salients respect to reentrants

Lower Crust, Pinched Out, Zagros